MAX8855ETJ+ Maxim Integrated Products, MAX8855ETJ+ Datasheet

MAX8855ETJ+

Manufacturer Part Number

MAX8855ETJ+

Description

IC REG STP DWN DUAL 5A 32-TQFN

Manufacturer

Maxim Integrated Products

Type

Step-Down (Buck)r

Datasheet

1.MAX8855ETJ.pdf (20 pages)

Specifications of MAX8855ETJ+

Internal Switch(s)

Yes

Synchronous Rectifier

Number Of Outputs

Voltage - Output

0.6 ~ 3.24 V

Current - Output

Frequency - Switching

500kHz ~ 2MHz

Voltage - Input

2.35 ~ 3.6 V

Operating Temperature

-40°C ~ 85°C

Mounting Type

Surface Mount

Package / Case

32-TQFN Exposed Pad

Power - Output

2.76W

Output Current

5 A

Input Voltage

2.35 V to 3.6 V

Supply Current

2.8 mA

Switching Frequency

2 MHz

Mounting Style

SMD/SMT

Maximum Operating Temperature

+ 85 C

Minimum Operating Temperature

- 40 C

Lead Free Status / RoHS Status

Lead free / RoHS Compliant

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The MAX8855 high-efficiency, dual step-down regulator

is capable of delivering up to 5A at each output. The

device operates from a 2.35V to 3.6V supply, and pro-

vides output voltages from 0.6V to 0.9 x V

ideal for on-board point-of-load applications. Total output

error is less than ±1% over load, line, and temperature.

The MAX8855 operates in PWM mode with a switching

frequency ranging from 0.5MHz to 2MHz, set by an

external resistor. It can also be synchronized to an

external clock in the same frequency range. Two inter-

nal switching regulators operate 180° out-of-phase to

reduce the input ripple current, and consequently

reduce the required input capacitance. The high

operating frequency minimizes the size of external

components. High efficiency, internal dual-nMOS

design keeps the board cool under heavy loads. The

voltage-mode control architecture and the high-band-

width (> 15MHz typ) voltage-error amplifier allow a type

III compensation scheme to be utilized to achieve fast

response under both line and load transients, and also

allow for ceramic output capacitors.

Programmable soft-start reduces input inrush current.

Two enable inputs allow the turning on/off of each out-

put individually, resulting in great flexibility for system-

level designs. A reference input is provided to facilitate

output-voltage tracking applications. The MAX8855 is

available in a 32-pin thin QFN (5mm x 5mm) package

with 0.8mm max height.

19-0726; Rev 2; 4/09

Pin Configuration appears at end of data sheet.

For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,

or visit Maxim’s website at www.maxim-ic.com.

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________________________________________________________________ Maxim Integrated Products

General Description

Dual, 5A, 2MHz Step-Down Regulator

Applications

, making it

o 27mΩ On-Resistance Internal MOSFETs

o Dual, 5A, PWM Step-Down Regulators

o Fully Protected Against Overcurrent,

o ±1% Output Accuracy Over Load, Line,

o Operates from 2.35V to 3.6V Supply

o REFIN on One Channel for Tracking or

o Integrated Boost Diodes

o Adjustable Output from 0.6V to 0.9 x V

o Soft-Start Reduces Inrush Supply Current

o 0.5MHz to 2MHz Adjustable Switching,

o All-Ceramic-Capacitor Design

o 180° Out-of-Phase Operation Reduces Input

o Individual Enable Inputs and PWRGD Outputs

o Safe-Start into Prebiased Output

o Available in 5mm x 5mm Thin QFN Package

o Sink/Source Current in DDR Applications

+ Denotes a lead(Pb)-free/RoHS-compliant package.

* EP = Exposed pad.

MAX8855ETJ+

OUTPUT1

1.2V / 5A

Short Circuit, and Overtemperature

and Temperature

External Reference

or FSYNC Input

Ripple Current

PART

OFF

TYPE III

COMPENSATION

2.35V TO 3.6V

INPUT1

Typical Operating Circuit

-40°C to +85°C

TEMP RANGE

Ordering Information

BST1

LX1

PGND1

FB1

COMP1

PWRGD1 PWRGD2

EN1

MAX8855

IN1 IN2

GND

COMP2

PGND2

BST2

EN2

LX2

FB2

TYPE III

COMPENSATION

INPUT2

2.35V TO 3.6V

PIN-PACKAGE

32 Thin QFN-EP*

OFF

Features

OUTPUT2

1.5V / 5A

Related parts for MAX8855ETJ+

MAX8855ETJ+ Summary of contents

Page 1

... All-Ceramic-Capacitor Design o 180° Out-of-Phase Operation Reduces Input Ripple Current o Individual Enable Inputs and PWRGD Outputs o Safe-Start into Prebiased Output o Available in 5mm x 5mm Thin QFN Package o Sink/Source Current in DDR Applications PART MAX8855ETJ+ + Denotes a lead(Pb)-free/RoHS-compliant package. Applications * EP = Exposed pad. OUTPUT1 1. OFF Features ...

Page 2

Dual, 5A, 2MHz Step-Down Regulator ABSOLUTE MAXIMUM RATINGS IN_, LX_ VDL, PWRGD_ to GND..................-0.3V to +4. VDL to IN_.....................................................-0.3V to +4.5V DD EN_, SS_, COMP_, FB_, REFIN, FSYNC to GND ......-0.3V to the lower of ...

Page 3

Dual, 5A, 2MHz Step-Down Regulator ELECTRICAL CHARACTERISTICS (continued 3.3V 0.5V, V IN_ VDD VDL FB_ C = 0.022µF, PWRGD_ not connected; T SS_ PARAMETER REFIN, SS2 REFIN Input Bias Current REFIN Common-Mode ...

Page 4

Dual, 5A, 2MHz Step-Down Regulator ELECTRICAL CHARACTERISTICS (continued 3.3V 0.5V, V IN_ VDD VDL FB_ C = 0.022µF, PWRGD_ not connected; T SS_ PARAMETER FSYNC FSYNC Capture Range FSYNC Input Threshold FSYNC ...

Page 5

Dual, 5A, 2MHz Step-Down Regulator ( 3.3V. MAX8855, circuit of Figure 6, T IN1 IN2 SWITCHING FREQUENCY vs. TEMPERATURE 1100 1080 1060 1040 1020 1000 980 960 940 920 900 -40 -15 10 AMBIENT TEMPERATURE (°C) SHUTDOWN ...

Page 6

Dual, 5A, 2MHz Step-Down Regulator ( 3.3V. MAX8855, circuit of Figure 6, T IN1 IN2 OUTPUT PEAK CURRENT LIMIT vs. OUTPUT VOLTAGE 0.8 1.1 1.4 1.7 2.0 2.3 ...

Page 7

Dual, 5A, 2MHz Step-Down Regulator PIN NAME Power-Good Open-Drain Output for Regulator 1. PWRGD1 is high impedance when V ≥ 0 PWRGD1 V FB1 REFIN thermal shutdown is activated, or when V External Reference Input for Regulator ...

Page 8

Dual, 5A, 2MHz Step-Down Regulator PIN NAME Power-Supply Input for Regulator 1. The voltage range is 2.35V to 3.6V. Connect two 10µF and one 0.1µF 27, 28 IN1 ceramic capacitors from IN1 to PGND1. Enable Input for Regulator 1. Drive ...

Page 9

Dual, 5A, 2MHz Step-Down Regulator V DD SHUTDOWN CONTROL BIAS GENERATOR EN1 EN2 VOLTAGE REFERENCE SS1 SOFT-START 1 SS2 SOFT-START 2 + REFIN - FB1 ERROR AMPLIFIER COMP1 COMP LOW DETECTOR FROM SS2 (0.6V FB2 ERROR AMPLIFIER COMP2 ...

Page 10

Dual, 5A, 2MHz Step-Down Regulator The power-good, open-drain output for regulator 2 (PWRGD2) is high impedance when V ≥ 0 PWRGD2 is low when V FB2 SS2 EN2 is low below V ...

Page 11

Dual, 5A, 2MHz Step-Down Regulator For ratiometric tracking applications, connect REFIN to the center of a voltage-divider from the output of regula- tor 2 to GND (see Figure 3b). In this application, the EN_ inputs are connected to each other ...

Page 12

Dual, 5A, 2MHz Step-Down Regulator Figure 3d. Startup and Sequencing Options—Matching Startup Slopes of Output Voltages with Internal Reference In Figure 3d, EN1 and EN2 are connected together and driven as a single input. Although both outputs begin ramping up ...

Page 13

Dual, 5A, 2MHz Step-Down Regulator In DDR tracking applications such as Figure 7, the FB1 regulation voltage tracks the voltage at REFIN. In Figure 7, the output of regulator 1 tracks V of the output voltages is set as follows: ...

Page 14

Dual, 5A, 2MHz Step-Down Regulator Output-Capacitor Selection The key selection parameters for the output capacitor are capacitance, ESR, ESL, and voltage-rating require- ments. These affect the overall stability, output ripple voltage, and transient response of the DC-DC convert- er. The ...

Page 15

Dual, 5A, 2MHz Step-Down Regulator π × × π × × π × ...

Page 16

Dual, 5A, 2MHz Step-Down Regulator Set the second compensation pole at 1/2 the switching frequency. Calculate C10 as follows π × × The recommended range for R4 is 2kΩ to 10kΩ. Note ...

Page 17

Dual, 5A, 2MHz Step-Down Regulator INPUT 2.35V TO 3. 10µF 0.1µF C4 C18 L1 0.1µF 47µF OUT1 0.56µH 0.1µF 1.2V/ 200Ω 10kΩ C11 330pF 10kΩ 1000pF R6 10kΩ C10 OPEN 0.022µF ...

Page 18

Dual, 5A, 2MHz Step-Down Regulator INPUT 2. 10µF 0.1µF C4 C18 L1 0.1µF 47µF OUT1 1µH 0.1µF 0.9V/ 200Ω C9 10kΩ R7 C11 330pF 10kΩ 1000pF OUT2 C10 R1 OPEN 1kΩ R19 ...

Page 19

Dual, 5A, 2MHz Step-Down Regulator Pin Configuration TOP VIEW PGND1 25 PGND1 26 27 IN1 28 IN1 MAX8855 EN1 29 COMP1 30 31 FB1 + 32 SS1 THIN ...

Page 20

... Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. 20 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 © 2009 Maxim Integrated Products DESCRIPTION Maxim is a registered trademark of Maxim Integrated Products, Inc ...

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